Police are investigating a small explosion that led to the evacuation of a Starbucks coffee shop.

No injuries were reported and police said the only damage was minor charring on the floor.

Investigators believe someone set off a homemade incendiary device in a plastic soda bottle as a prank Thursday night, police Maj. Thomas Oates said

About 25 people were in the shop on the city's East Side when the explosion happened.

Starbucks spokeswoman Deb Trevino said the company received no phone calls, threats or other information that would lead them to believe they were targeted by a bomb maker.